Light beam imaging apparatus, such as laser imaging apparatus, are widely used in applications in which an information medium (such as film, paper, stimulable storage phosphor) is scanned to produce an electronic image signal or in which an electronic image signal is reproduced in a photosensitive medium, such as film. Typically, the laser beam is scanned by an oscillating mirror or multifaceted polygon scanner (mirror) in a line direction across the medium as the medium is moved in a direction perpendicular to the line scan direction. Where a multifaceted polygon scanner is used, facet to facet errors may result in undesirable line to line variations in the scanned or reproduced image. Such variations cause image artifacts and degradation. The following patents disclose various proposals to correct for facet-to-facet errors relating to laser beam spot size, laser beam scanning speed, clock frequency, etc., but not for facet-to-facet reflectance errors.
U.S. Pat. No. 4,257,053, issued Mar. 17, 1981, inventor C. R. Gilbreath;
U.S. Pat. No. 4,204,233, issued May 20, 1980, inventor G. E. Swager;
U.S. Pat. No. 4,320,420, issued Mar. 16, 1981, inventor R. E. Rider;
U.S. Pat. No. 4,717,925, issued Jan. 5, 1988, inventors I. Shibata et al.;
U.S. Pat. No. 4,833,489, issued May 23, 1989, inventor C. Byung-Sik; and
U.S. Pat. 4,733,064, issued Mar. 22, 19899, inventor H. Ishikawa.
It is thus desirable in a light beam imaging apparatus using a multifaceted polygon scanner to provide facet-to-facet reflectance correction in order to effect uniform line-to-line scanning and to minimize image artifacts and degradation resulting from facet reflectance differences.